As a system for implementing an FMC service by using Internet Protocol (IP), a UMA (unlicensed mobile access) system has been used as a standard. In the UMA standard, an Internet connection service is provided in which a portable terminal is connected to a home AP (access point) to use a broadband network, and a portable terminal serving as a non-IP terminal is connected through an IPsecGW apparatus called a UNC (unlicensed network controller) when the FMC service is provided in which a VPN (virtual private network) service is provided. The UMA system performs the following processing, for example, to accommodate a portable terminal not conforming to IP in an IP access network.
A portable terminal conforming to a UMA standard capsulates an existing communication protocol for portable telephones by IPsec Protocol (IP Security Protocol) and sends it to a GW (gateway) apparatus called the UNC. The UNC terminates IPsec Protocol to take out the portable-telephone protocol which has been capsulated and connects it to an existing portable telephone network based on the telephone routing. By using IPsec Protocol, an Internet connection service can be provided while the same level of security as with usual portable telephones is provided even through the Internet. The technical specifications of the UMA is disclosed, for example, in www.umatechnology.org (non-patent document 1). In particular, the UMA Architecture (stage 2) document (non-patent document 2) discloses in detail the tunneling specifications of a portable telephone protocol using IPsec Protocol. Basically, an FMC terminal is a mobile terminal, but when used in a home, the FMC terminal can use a service through a fixed Internet as if it were a fixed terminal.
When communication business parties such as carriers do not provide the FMC service as an open service on the Internet in order to corral their customers, a combination with the VPN technology, which provides private services, is important. As for VPN software for connecting remote networks by using the VPN technology, introduction articles about creating Internet VPN environments such as VTun (virtual tunnel) and OpenVPN are published in UNIX Magazine Vol. 7 in 2004 and Vol. 8 in 2004 (non-patent document 3). By using software for Vtun or the like, a service can be provided which acts as if remote terminals and servers existed in an identical LAN (local area network).
A path control method used in a network where a plurality of paths can be selected is disclosed in which a terminal is connected to a destination address by a default path specified in advance (see patent document 1, for example).    Non-patent document 1: www.umatechnology.org    Non-patent document 2: UMA Architecture (stage 2) Document    Non-patent document 3: UNIX Magazine Vol. 7 in 2004 and Vol. 8 in 2004    Non-patent document 4: L2TPv2 (RFC 2661)    Non-patent document 5: L2TPv3 (RFC 3931)    Patent document 1: Japanese Unexamined Patent Application Publication No. Hei-11-112570